MBS Protocol
PLX3x Series ♦ Multi-Protocol Gateways
User Manual
Page 122 of 215
ProSoft Technology, Inc.
January 25, 2018
MBS Master Configuration Parameters
Parameter
Value
Description
Response
Timeout
0 to 65535
Specifies the command response timeout period in 1 millisecond increments.
This is the time that a port configured as a Master waits for a response from
the addressed slave before re-transmitting the command or skipping to the
next command in the Command List (see
Retry Count
). The value to specify
depends on the communication network and the expected response time
(plus or minus) of the slowest device on the network.
Retry Count 0 to 10
Specifies the number of times the gateway retries a command if it fails.
End of
Message
Delay
0 to 65535
Specifies a time delay in milliseconds added to the 3.5 character time delay
used by the module to recognize the end of a message. Certain applications
may require validation of Modbus messages with more than 3.5 character
time between consecutive bytes (for example, modem applications). A value
of 0 causes the gateway to use the default end of message delay.
Minimum
Command
Delay
0 to 32767
Specifies the number of milliseconds the gateway waits between receiving
the end of a slave's response to the most recently transmitted command and
the issuance of the next command. You can use this parameter to place a
delay after each command to avoid sending commands on the network faster
than the slaves can receive them. This parameter does not affect retries of a
command, as the gateway issues retries when a command failure is
recognized.
Error Delay
Counter
0 to 60000
Specifies the number of poll attempts to be skipped before trying to re-
establish communications with a slave that has failed to respond to a
command within the time limit set by
Response Timeout
. After the slave fails
to respond, the master skips sending commands that would have been sent
to the slave until the number of skipped commands matches the value
entered in this parameter. This creates a sort of
slow poll mode
for slaves
that are experiencing communication problems.
Command
Control Reg
-1, 0 to 3900 This parameter allows the execution of commands in the Command List to be
controlled by setting a value of zero (0), one (1), two (2), or three (3) into a
100-register area of the gateway database, beginning at the address entered
in this parameter.
If you specify an Enable code of zero (0) for all the commands in the list,
then no commands are executed.
If you change the value in the first control register to one (1), the
gateway executes command zero continuously.
If you set the value is the control register for a write command two (2),
the command is enabled for conditional writing, which causes the
gateway to execute the command whenever the values in the database
registers associated with the command change. Use the value of three
(3) only for bit-level write commands, FC 5 and 15. If you set the
parameter to three (3), the command is executed only if the internal bit
data associated with the command changes. It also clears the bit or bits
in the internal database after the write command is built.
To use this feature, configure the commands as disabled (enable code =
0).
This Command Control feature can be disabled by setting this parameter
to a value of 0 to -1.
For information on the Command List, see MBS Port [x] Commands (page
124).
